WASHINGTON _ When the Smithsonian’s National Museum of the American Indian opens Sept. 21, there will be no mistaking it for a holocaust museum. It is too light, too airy, too bright a celebration of a people’s cultural bounty to brood about their brush with extinction.

And yet, for Suzan Shown Harjo, a founding trustee, this final addition to the hallowed civic green of the National Mall can’t help but commemorate the millions of indigenous lives lost since the “discovery” of America in 1492.

“You can’t tell the story of native people without telling that story too,” said Harjo, an Indian rights activist here. “People need to know how close a call it was for the rest of us.”

And so begins debate over how best to characterize what happened to American Indians. Inevitably, the question arises: Was it genocide?

“I don’t know how to explain it otherwise,” said Ben Nighthorse Campbell, the Colorado Republican who is the only American Indian in the U.S. Senate and who initiated the legislation to create the museum. “It was genocide.”

No, concludes Guenter Lewy, who engages the question in the September issue of Commentary magazine, the neoconservative journal published by the American Jewish Committee.

“In the end, the sad fate of America’s Indians represents not a crime but a tragedy, involving an irreconcilable collision of cultures, and values,” writes Lewy, an professor emeritus of political science at the University of Massachusetts and the author of books on the Nazi persecution of Gypsies and the role of the German Catholic Church in the Holocaust.

Crime or calamity? The debate has raged in academic and activist circles for years, especially since the Columbus Quincentenary in 1992, and ultimately cuts to the quick of American identity and the nation’s moral self-image.

In the estimation of David Stannard, “the European conquest of the New World, including the U.S. government’s destruction of its own native peoples, was the most massive interrelated sequence of genocides in the history of the world.” Stannard, a professor of American studies at the University of Hawaii, is the author of “American Holocaust: The Conquest of the New World,” published in 1992.

But James Axtell, in “Beyond 1492: Encounters in Colonial North America,” published the same year, argues that to sweepingly apply “genocide” to centuries of innumerable, disparate encounters across a continent between all manner of Europeans and hundreds of very different Indian tribes is slipshod history.

“You don’t have very many cases over that 500 years where the whole population of single Indian groups were targeted for annihilation,” said Axtell, a historian at the College of William & Mary.

It is of more than academic interest.

In May, Sen. Sam Brownback, R-Kan., introduced a resolution, co-sponsored by Campbell and three other senators and timed to the museum’s opening, apologizing to the American Indians on behalf of the U.S. government.

Brownback avoids the label “genocide.” “I don’t think that’s useful,” he said. But his resolution refers bluntly to the “broken treaties and many of the more ill-conceived federal policies that followed, such as extermination, termination, forced removal and relocation, the outlawing of traditional religions, and the destruction of sacred places.”

Brownback was motivated by “this deep root of bitterness” among American Indians in his home state. But he also well knows that when his friend, former Rep. Tony Hall, D-Ohio, introduced legislation in 2000 to apologize for slavery, it was quickly swallowed up in a tempest of controversy and concerns that it would lead to reparations.

If anything, the treatment of Indians could provoke more fundamental, if less frequently considered, questions about the meaning of America. Slavery has been called the nation’s original sin, its most glaring failure to live up to its founding creed. But if America was not only built on slavery but had its genesis in genocide, then what?

“Innocent Americans?” asks Ward Churchill, who chairs the Ethnic Studies Department at the University of Colorado in Boulder. The phrase is in wide use since Sept. 11, he offered. But, what, in view of the treatment of America’s native peoples, can it mean?

Before Osama bin Laden and Saddam Hussein there was Sir Jeffrey Amherst, the commander in chief of British forces in America who in 1763 wrote Col. Henry Bouquet at Fort Pitt in Pennsylvania recommending that he spread smallpox-infected blankets among the Indians, “as well as to try every other method that can serve to extirpate this execrable race.”

“Look in the goddamn mirror,” said Churchill, author of “A Little Matter of Genocide: Holocaust and Denial in the Americas, 1492 to the Present.”

This much is agreed upon: At the nadir, in 1900, there were fewer than 250,000 Indians living in the United States. Just what their population was in 1492 is in dispute.

“The only sensible figure is between 21/2 and 4 million north of Mexico,” said Axtell. UCLA anthropologist Russell Thornton, in “American Indian Holocaust and Survival: A Population History Since 1492,” estimates the population in what is now the United States topped 5 million. In remarks at the National Press Club when the museum broke ground in 1999, W. Richard West Jr., the museum’s director, put the figure in the 6 million to 9 million range. Stannard and others suggest it could be even higher.

Regardless, over the centuries the American Indian population was decimated by 90 percent or more as a consequence of war, deprivation, starvation, displacement, massacres and disease, of conquest by the white men who viewed them to be, much as the Declaration of Independence described them, “merciless Indian savages.”

More than a century later, Theodore Roosevelt, who was president at their lowest ebb, had no less dim a view of Indian humanity.

“I don’t go so far as to think that the only good Indians are dead Indians, but I believe nine out of 10 are, and I shouldn’t like to inquire too closely into the case of the 10th,” said Roosevelt, who, adding insult to injury, has his visage carved into Mount Rushmore, held sacred by the Sioux.

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And yet, Lewy and others argue that overall the treatment of American Indians does not meet the genocide standard established by the United Nations, which requires that the acts were “committed with intent to destroy in whole or in part, a national, ethnic, racial or religious group as such.”

The European conquest of the New World may have been “monumentally destructive,” writes Steven Katz, a Boston University professor and author of “The Holocaust in Historical Context.” But, Katz contends, mass death was “almost without exception caused by microbes, not militia. … This depopulation happened unwittingly rather than by design.”

But, said Thornton, a Cherokee, that doesn’t mean there weren’t occasions of genocide _ the massacres at Wounded Knee in South Dakota in 1890, or at Sand Creek in the Colorado Territory in 1864, where both Harjo and Campbell lost ancestors, or a spate of events that lay waste to the Indian population in northern California and southern Oregon Territory in the mid-19th century.

Altogether, Thornton said, the white mind-set was not quite genocidal: “It was not really the only good Indian is a dead Indian. It was really the only good Indian is somewhere else. If you have to kill them, fine. If you can move them, fine. Just get rid of them.”

As West, who is Cheyenne and Arapaho, put it in his press club remarks, “At the time, native peoples were simply in the way of your American expansion and the quest for national and personal treasure.”

The museum expects 4 million visitors its first year _ just about the number of Americans who counted themselves as all or part Indian in the 2000 Census. The spirit of the place will be one of renaissance.

Harjo believes that in the end, it won’t obscure the true history, but will lead people to ask the questions that will reveal it.

“No matter how prettily this is wrapped, this story is going to be told because there are living people who are the survivors of the genocide that was attempted on all of us,” she said. “Everyone had a massacre in their history. Everyone had a long walk.”